In this study, we first report the development of a robust and efficient finite volume based adsorption process simulator, essential for rigorous optimization of a transient cyclic operation without resorting to any model reduction. We present a detailed algorithm for the common boundary conditions encountered in nonisothermal and nonisobaric adsorption process simulations. A comprehensive comparison of the high-resolution total variation diminishing (TVD) schemes, namely, van Leer and Superbee, with the weighted essentially nonoscillatory (WENO) finite volume scheme is performed, and trade-off plots are presented to identify the numerical scheme most suitable for attaining speed and accuracy at the same time. The simulator is then used to perform rigorous optimization of a four-step process for postcombustion CO2 capture from dry flue gas on zeolite 13X. The aim is to identify operating conditions at which the purity and recovery demands are met and to calculate corresponding energy consumption and process productivity. The purity–recovery and energy–productivity Paretos are generated using multiobjective optimization. It is shown that, for a strict vacuum swing adsorption (VSA) process, an evacuation pressure of 0.02 bar is required to satisfy regulatory demands of attaining a CO2 purity and recovery of 90%. It is also quantitatively shown that pressurizing the flue gas is detrimental to the energy consumption of process, although offering improvement in productivity.

The capture and concentration of CO 2 from a dry flue gas by vacuum swing adsorption (VSA) has been experimentally demonstrated in a pilot plant. The pilot plant has the provision for using two coupled columns that are each packed with approximately 41 kg of Zeochem zeolite 13X. Breakthrough experiments were first carried out by perturbing a N 2 saturated bed with 15% CO 2 and 85% N 2 feed, which is representative of a dry flue gas from coal-fired power plants. The breakthrough results showed long plateaus in temperature profiles confirming a near adiabatic behavior. In the process study, a basic four-step vacuum swing adsorption (VSA) cycle comprising the following steps: pressurization with feed, adsorption, forward blowdown, and reverse evacuation was investigated first. In the absence of any coupling among the steps, a single bed was used. With this cycle configuration, CO 2 was concentrated to 95.9 6 1% with a recovery of 86.4 6 5.6%. To improve the process performance, a four-step cycle with light product pressurization (LPP) using two beds was investigated. This cycle was able to achieve 94.8 6 1% purity and 89.7 6 5.6% recovery. The Department of Energy requirements are 95% purity and 90% recovery. The proposed underlying physics of performance improvement of the four-step cycle with LPP has also been experimentally validated. The pilot plant results were then used for detailed validation of a one-dimensional, nonisothermal, and nonisobaric model. Both transient profiles of various measured variables and cyclic steady state performance results were compared with the model predictions, and they were in good agreement. The energy consumptions in the pilot plant experiments were 339-583 6 36.7 kWh tonne 21 CO 2 captured and they were significantly different from the theoretical power consumptions obtained from isentropic compression calculations. The productivities were 0.87-1.4 6 0.07 tonne CO 2 m 23 adsorbent day 21. The results from our pilot plant were also compared with available results from other pilot plant studies on CO 2 capture from flue gas.

No abstract

No abstract

in Wiley InterScience (www.interscience.wiley.com).The novel feature of the presented simulated moving bed (SMB) controller is its capability to make use of the average outlet concentration of the product streams over a cycle as feedback information, i.e., 'cycle to cycle' control. Its effectiveness is confirmed experimentally on an eight-column four-section laboratory SMB unit, which is used to separate a binary mixture of the nucleosides, uridine and guanosine. The performance of the 'cycle to cycle' SMB control scheme is also demonstrated by several SMB simulation runs that are chosen to test the robustness of the controller. Furthermore, the case where measurements have a time delay is presented. The results illustrate that the 'cycle to cycle' controller is able to meet the products' purity specifications and operate the process optimally with minimal information about the system regardless of the disturbances that might take place during the operation.Note that Y k contains the concentrations of both species for every time step n 5 0, . . ., N 2 1 of cycle k. Figure 4. Performance of the controller on the laboratory SMB plant for case studies 1 and 2. Outlet purities and cost function vs. time measured in cycles. Feed pump delivers 10% more than its set point after cycle 70. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]